1. Field of the Invention
This invention relates to novel hydroxyaromatic compounds. More particularly, this invention relates to novel poly (oxyalkylene) hydroxyaromatic esters and their use in fuel compositions to prevent and control engine deposits.
2. Description of the Related Art
It is well known that automobile engines tend to form deposits on the surface of engine components, such as carburetor ports, throttle bodies, fuel injectors, intake ports and intake valves, due to the oxidation and polymerization of hydrocarbon fuel. These deposits, even when present in relatively minor amounts, often cause noticeable driveability problems, such as stalling and poor acceleration. Moreover, engine deposits can significantly increase an automobile's fuel consumption and production of exhaust pollutants. Therefore, the development of effective fuel detergents or "deposit control" additives to prevent or control such deposits is of considerable importance and numerous such materials are known in the art.
For example, aliphatic hydrocarbon-substituted phenols are known to reduce engine deposits when used in fuel compositions. U.S. Pat. No. 3,849,085, issued Nov. 19, 1974 to Kreuz et al., discloses a motor fuel composition comprising a mixture of hydrocarbons in the gasoline boiling range containing about 0.01 to 0.25 volume percent of a high molecular weight aliphatic hydrocarbon-substituted phenol in which the aliphatic hydrocarbon radical has an average molecular weight in the range of about 500 to 3,500. This patent teaches that gasoline compositions containing minor amount of an aliphatic hydrocarbon-substituted phenol not only prevent or inhibit the formation of intake valve and port deposits in a gasoline engine, but also enhance the performance of the fuel composition in engines designed to operate at higher operating temperatures with a minimum of decomposition and deposit formation in the manifold of the engine.
Similarly, U.S. Pat. No. 4,134,846, issued Jan. 16, 1979 to Machleder et al., discloses a fuel additive composition comprising a mixture of (1) the reaction product of an aliphatic hydrocarbon-substituted phenol, epichlorohydrin and a primary or secondary mono- or polyamine, and (2) a polyalkylene phenol. This patent teaches that such compositions show excellent carburetor, induction system and combustion chamber detergency and, in addition, provide effective rust inhibition when used in hydrocarbon fuels at low concentrations.
Fuel additives containing a poly(oxyalkylene) moiety are also known in the art. For example, U.S. Pat. No. 4,191,537, issued Mar. 4, 1980 to R. A. Lewis et al., discloses a fuel composition comprising a major portion of hydrocarbons boiling in the gasoline range and from 30 to 2000 ppm of a hydrocarbyl poly(oxyalkylene) aminocarbamate having a molecular weight from about 600 to 10,000, and at least one basic nitrogen atom. The hydrocarbyl poly(oxyalkylene) moiety is composed of oxyalkylene units selected from 2 to 5 carbon oxyalkylene units. These fuel compositions are taught to maintain the cleanliness of intake systems without contributing to combustion chamber deposits.
Aromatic compounds containing a poly(oxyalkylene) moiety are also known in the art. For example, the above-mentioned U.S. Pat. No. 4,191,537, discloses alkylphenyl poly(oxyalkylene) polymers which are useful as intermediates in the preparation of alkylphenyl poly(oxyalkylene) aminocarbamates.
Additionally, hydroxyaromatic compounds containing a poly(oxyalkylene) moiety are known in the art. For example, U.S. Pat. No. 4,952,732, issued Aug. 28, 1990 to G. P. Speranza et al., discloses Mannich condensates prepared from a phenol, formaldehyde and an alkylamine containing propoxy groups and, optionally, ethoxy groups. These Mannich condensates are taught to be useful as corrosion inhibitors, water repellent agents, paint adhesion promotors, and also as intermediates for preparing surfactants, and pololys finding use in the manufacture of polyurethane foam.
It has now been discovered that certain hydroxyaromatic esters having a poly(oxyalkylene) "tail" provide excellent control of engine deposits, especially intake valve deposits, when employed as fuel additives in fuel compositions. Moreover, these poly(oxyalkylene) hydroxyaromatic esters have been found to produce fewer combustion chamber deposits than known aliphatic hydrocarbon-substituted phenolic fuel additives.